The compound [1S-(1α, 2α, 3β(1S*,2R*),5β)]-3-[7-[2-(3,4-difluorophenyl)-cyclopropyl]amino]-5-(propylthio)-3H-1,2,3-triazolo[4,5-d]pyrimidin-3-yl)-5-(2-hydroxyethoxy)-cyclopentane-1,2-diol (Compound A), and similar such compounds, are disclosed in WO 00/34283 and WO 99/05143. These compounds are disclosed as P2T (which is now usually referred to as P2Y12) receptor antagonists. Such antagonists can be used as, inter alia, inhibitors of platelet activation, aggregation or degranulation.
We have now found an advantageous process for preparing enantiomerically pure trans-cyclopropane carboxylic acid derivatives which may be used in the preparation of Compound A. The process offers advantages such as, for example: diastereoselecivity, enantioselectivity, high yield, potential for manufacturing (e.g. reagents and procedures suitable for large scale production, non-hazardous reagents, less waste).